Postglacial range expansion shaped the spatial genetic structure in a marine habitat‐forming species: Implications for conservation plans in the Eastern Adriatic Sea
Jean‐Baptiste LedouxMaša Frleta‐ValićSilvija KipsonAgostinho AntunesEmma CebriánCristina LinaresPablo SánchezRaphaël LebloisJoaquim Garrabou
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Abstract Aim Understanding how historical and contemporary processes shaped and maintain spatial patterns of genetic diversity is a major goal for conservation biologists. Here, we characterized the pattern of neutral genetic diversity and we inferred underlying processes in the habitat‐forming octocoral Paramuricea clavata in the Adriatic Sea, a peculiar phylogeographic region of the Mediterranean Sea. Location Eastern coast of the Adriatic Sea. Methods We genotyped seven microsatellites in 454 individuals of P. clavata from 13 populations recolonized after the Last Glacial Maximum ( LGM ). We estimated the levels of contemporary connectivity and genetic drift and we reconstructed the demographic history of these populations. Results The pattern of spatial genetic structure resulted from the combination of hierarchical genetic clusters and isolation by distance ( IBD ). A significant decrease in genetic diversity and an increase of the frequencies of individual alleles likely due to allele surfing from the south to the north of the area were observed as expected after a postglacial sequential recolonization. Based on maximum likelihood analyses, the foundation of these populations was not linked to dramatic change in population size. Main conclusion Oceanographic barriers to gene flow combined to the restricted dispersal of P. clavata likely maintain the hierarchical structure and the IBD pattern. We suggest that the latitudinal genetic gradient results from a northward “serial founder events” recolonization. By integrating patterns and processes, we bridge the gap between the evolutionary and the conservation biology of P. clavata , providing management guidelines, which will benefit the associated coralligenous biodiversity.Keywords:
Last Glacial Maximum
Isolation by distance
Conservation Genetics
Marine protected area
Summary The free‐living planktonic freshwater bacterium P olynucleobacter necessarius subspecies asymbioticus (> 99% 16 S rRNA similarity) represents a taxon with a cosmopolitan distribution and apparently ubiquitous occurrence in lentic freshwater habitats. We tested for intra‐taxon biogeographic patterns by combining cultivation‐independent and cultivation methods. A culture collection of 204 strains isolated from globally distributed freshwater habitats ( A rctic to A ntarctica) was investigated for phylogeographic patterns based on sequences of two markers, the 16 S –23 S internal transcribed spacers and the glutamine synthetase gene ( glnA ). Genetic distance between isolates showed significant geographic distance‐decay patterns for both markers, suggesting that an isolation‐by‐distance mechanism influences the global phylogeography. Furthermore, a couple of subgroups showed restricted geographic distributions. Strains of one subgroup were exclusively obtained from tropical sites on four continents (pantropical subgroup). Cultivation‐independent methods were used to confirm the restricted geographic distributions of two subgroups. The pantropical taxon could be detected in 63% of investigated tropical habitats but not in any of 121 E uropean freshwater samples. Physiological tests indicated that almost all strains of the pantropical subgroup failed to grow at temperatures of 4°C, while strains affiliated with other subgroups showed good growth at this temperature. This suggests that thermal adaptation is involved in phylogeographic structuring of the global P olynucleobacter population.
Pantropical
Subspecies
Isolation by distance
Cosmopolitan distribution
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Although a number of studies have assessed the effects of geological and climatic changes on species distributions in East Asian, we still have limited knowledge of how these changes have impacted avian species in south-western and southern China. Here, we aim to study paleo-climatic effects on an East Asian bird, two subspecies of black-throated tit (A. c. talifuensis–concinnus) with the combined analysis of phylogeography and Ecological Niche Models (ENMs). We sequenced three mitochondrial DNA markers from 32 populations (203 individuals) and used phylogenetic inferences to reconstruct the intra-specific relationships among haplotypes. Population genetic analyses were undertaken to gain insight into the demographic history of these populations. We used ENMs to predict the distribution of target species during three periods; last inter-glacial (LIG), last glacial maximum (LGM) and present. We found three highly supported, monophyletic MtDNA lineages and different historical demography among lineages in A. c. talifuensis–concinnus. These lineages formed a narrowly circumscribed intra-specific contact zone. The estimated times of lineage divergences were about 2.4 Ma and 0.32 Ma respectively. ENMs predictions were similar between present and LGM but substantially reduced during LIG. ENMs reconstructions and molecular dating suggest that Pleistocene climate changes had triggered and shaped the genetic structure of black-throated tit. Interestingly, in contrast to profound impacts of other glacial cycles, ENMs and phylogeographic analysis suggest that LGM had limited effect on these two subspecies. ENMs also suggest that Pleistocene climatic oscillations enabled the formation of the contact zone and thus support the refuge theory.
Last Glacial Maximum
Subspecies
Environmental niche modelling
Demographic history
Lineage (genetic)
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